1. Field of the Invention
This invention relates to the field of surgery, and more specifically to a device and method for guiding or applying force to a magnetic implant within the body of a patient.
2. Description of Related Art
It is known in the art to provide magnetic manipulation of diagnostic or therapeutic elements (which, for simplicity, we shall herein refer to collectively as xe2x80x9ctreatment implantsxe2x80x9d) through body tissue or ducts (such as in vascular exploration or treatment). Systems providing for such manipulation are described in a number of previously published articles and patents, such as xe2x80x9cMagnetically Guided Devices for Vascular Exploration and Treatment,xe2x80x9d Sadek K. Hilal et al., Radiology 113, 529-540 (1974); U.S. Pat. No. 3,358,676, entitled xe2x80x9cMagnetic Propulsion of Diagnostic or Therapeutic Elements Through the Body Ducts of Animals or Human Patients,xe2x80x9d issued Dec. 19, 1967 to Ephraim H. Frei et al.; xe2x80x9cMagnetic Manipulation Instrumentation for Medical Physics Research,xe2x80x9d George T. Gillies et al., Review of Scientific Instruments 65, 533-562 (1994); xe2x80x9cCharacteristics of an Improved Magnetic-Implant Guidance System,xe2x80x9d Robert G. McNeil et al., IEEE Trans. on Bio. Eng. 42(8) 802-808 (1995); xe2x80x9cFunctional Design Features and Initial Performance Characteristics of a Magnetic-Implant Guidance System for Stereotactic Neurosurgery,xe2x80x9d Robert G. McNeil et al., IEEE Trans. on Bio. Eng. 42(8) 793-801 (1995); and U.S. Pat. No. 5,654,864 to Ritter et al., entitled xe2x80x9cControl Method for Magnetic Stereotaxis System,xe2x80x9d issued Aug. 5, 1997. All of these references are hereby incorporated in their entirety by reference. These systems all provide fixed or manually moved permanent magnets or electromagnets that are capable of applying fields and forces to treatment implants to move or guide the implant through a treatment region. However, because the magnets or electromagnets for these systems are large, it is difficult or impossible to provide complex imaging systems that can operate in conjunction with the magnetic guidance system. In addition, because of the limited ability to move the magnets or electromagnets, it is difficult to apply fields and forces accurately directed at accurately known locations.
It is thus an object of the invention to provide a magnetic system for guiding the movement of a treatment implant in a treatment region of a body.
It is a further object of the invention to provide a magnetic guidance or propulsion system that permits complex and useful imaging systems to be used during magnetic guidance operation.
It is yet a further object of the invention to provide a magnetic guidance or propulsion system that permits complex and useful imaging systems to be used stereotactically and in an efficient manner during magnetic guidance operation.
It is yet another object of the invention to provide a method for performing magnetic guidance or propulsion of a treatment implant while simultaneously allowing complex and useful imaging systems to be used to help direct the guidance or propulsion of the treatment implant.
There is thus provided, according to a first aspect of the invention, an apparatus for producing a magnetic field to control a trajectory of a treatment implant in a treatment region of a body comprising: a bed configured to support a patient; a plurality of separately energizable electromagnets configured to produce magnetic fields of varying orientations in a treatment region of a patient supported by the bed; and a processor configured to control currents in subsets of the plurality of separately energizable electromagnets to generate a magnetic field having at least approximately a selected orientation and field strength. The bed may be moveable and controlled by a servo-system to aid in applying an accurately controlled magnetic field in the region of the treatment implant. In addition, one or more fluoroscopic or other medical imaging devices (which may or may not be fixed) may be provided, the illumination apparatus for which may be directed between gaps in the plurality of the coils, to provide a useful, effective, and possibly stereotactic display for a surgeon directing the surgery of the patient.
In another embodiment of the invention, the invention comprises an apparatus for producing a magnetic field to control a trajectory of a treatment implant in a treatment region of a body comprising: (a) a moveable bed configured to support a patient; (b) at least one medical imaging screen and medical imaging illuminator, which may or may not be fixed system, configured to provide a medical image of a patient supported by the moveable bed; (c) a set of electromagnets under the moveable bed, each configured to provide a magnetic field having different orientations in a treatment region of a patient supported by the moveable bed; (d) a servo control configured to move at least one of the bed or the set of electromagnets; and (e) a power source configured to selectively provide a selected amount of current to a subset of the set of electromagnets, the amount of current and the subset of the set of electromagnets being a function of time.
In yet another embodiment of the invention, the invention comprises a method for guiding an implant through a treatment region of a body comprising the steps of: (a) placing a body on a servo-controlled, moveable bed; (b) inserting a magnetically-guided treatment implant into the treatment region; (c) arranging a plurality of electromagnets around the treatment region so that a selected orientation of a magnetic at a location of the treatment implant can be approximated by selectively energizing a subset of the electromagnets, moving the bed, or both, as the case may be; (d) applying current to a selected subset of the plurality of electromagnets to provide a magnetic field at least approximating a selected magnitude and orientation at the location of the magnetically-guided treatment implant. During the applying step, medical imaging of the treatment region may be provided.
In one embodiment of the invention, a servo-controlled bed is provided for a patient. Preferably, but not necessarily, the bed is arranged for the patient to lie supine. One, or more preferably two or more fluoroscopes or other medical imaging devices are provided having screens above the supine body of the patient. A part of the body, which shall be referred to herein as the xe2x80x9ctreatment region,xe2x80x9d is to be placed below the screens of the fluoroscopes. An array of electromagnets, which may, but need not be superconducting, is provided and configured to provide, when one or more electromagnets are energized, an effective magnetic field in the treatment region of the body when the treatment region is below the screens of the fluoroscopes.
To place the treatment region of the body into the necessary position below the fluoroscopes, a computer or other servomechanism controls motion of the bed carrying the patient. Alternately, both the bed carrying the patient and the electromagnets may be moved. In an alternate embodiment of the invention, the bed and/or the electromagnets may be configured for manual movement as needed, if servo control is not provided for initial position of the patient, or as an optional alternative to servo control when it is provided.
In still another embodiment of the invention the electromagnets are replaced by permanent magnets, which may either be moved back and forth along their axes in order to change the overall field at the operating point in a patient, or they may employ shutter-like or keeper-like permeable material to organize the contributions of the individual magnets to the field at a particular location in a patient.